title: Sequential electron-transfer and proton-transfer pathways in hydride-transfer reactions from dihydronicotinamide adenine dinucleotide analogues to non-heme oxoiron(IV) complexes and p-chloranil. Detection of radical cations of NADH analogues in acid-promoted hydride-transfer reactions.
abstract: Hydride transfer from dihydronicotinamide adenine dinucleotide (NADH) analogues, such as 10-methyl-9,10-dihydroacridine (AcrH 2) and its derivatives, 1-benzyl-1,4-dihydronicotinamide (BNAH), and their deuterated compounds, to non-heme oxoiron(IV) complexes such as [(L)Fe (IV)(O)] (2+) (L = N4Py, Bn-TPEN, and TMC) occurs to yield the corresponding NAD (+) analogues and non-heme iron(II) complexes in acetonitrile. Hydride transfer from the NADH analogues to p-chloranil (Cl 4Q) also occurs to produce the corresponding NAD (+) analogues and the hydroquinone anion (Cl 4QH (-)). The logarithms of the observed second-order rate constants (log k H) of hydride transfer from NADH analogues to non-heme oxoiron(IV) complexes are linearly correlated with those of hydride transfer from the same series of NADH analogues to Cl 4Q, including similar kinetic deuterium isotope effects. The log k H values of hydride transfer from NADH analogues to non-heme oxoiron(IV) complexes are also linearly correlated with those of deprotonation of the radical cations of NADH analogues. Such linear correlations indicate that overall hydride-transfer reactions of NADH analogues to both non-heme oxoiron(IV) complexes and Cl 4Q occur via electron transfer from NADH analogues to the oxoiron(IV) complexes, followed by rate-limiting deprotonation from the radical cations of NADH analogues and subsequent rapid electron transfer from the deprotonated radicals to the Fe(III) complexes to yield the corresponding NAD (+) analogues and the Fe(II) complexes. The electron-transfer pathway was accelerated by the presence of perchloric acid, and the resulting radical cations of NADH analogues were detected by electron spin resonance spectroscopy and UV-vis spectrophotometry in the acid-promoted hydride-transfer reactions from NADH analogues to non-heme oxoiron(IV) complexes. This result provides the first direct evidence that a hydride transfer from NADH analogues to non-heme oxoiron(IV) complexes proceeds via an electron-transfer pathway.
authors.affiliation: Department of Material and Life Science, Graduate School of Engineering, Osaka University, SORST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan. fukuzumi@chem.eng.osaka-u.ac.jp
authors.forename: Shunichi
authors.initials: S
authors.lastname: Fukuzumi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kotani
authors.forename: Yong-Min
authors.initials: YM
authors.lastname: Lee
authors.forename: Wonwoo
authors.initials: W
authors.lastname: Nam
mesh_terms: D000166:Acridines / Q000737:chemistry; D002412:Cations / Q000737:chemistry; D002703:Chloranil / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry; D058085:Iron Compounds / Q000737:chemistry* / Q000145:classification*; D009243:NAD / Q000031:analogs & derivatives* / Q000737:chemistry; D010084:Oxidation-Reduction; D013056:Spectrophotometry, Ultraviolet
chemical_list: C445701:1-benzyl-1,4-dihydronicotinamide; C480178:10-methyl-9,10-dihydroacridine; D000166:Acridines; D002412:Cations; D005609:Free Radicals; D058085:Iron Compounds; D002703:Chloranil; D009243:NAD